Disc brake with plural pistons acting on one shoe

ABSTRACT

In a disc brake having a rotary disc with brake shoes on opposite sides, a cylinder block for moving the brake shoes includes at least three pistons all arranged on the same side of the disc and movable perpendicular to the disc, two pistons being movable in one direction and the other piston being movable in the opposite direction.

United States Patent 1 91 Maurice Oct. 23, 1973 [5 DISC BRAKE WITHPLURAL PISTONS 2,951,561 9/1960 Davis l88/73.4 X ACTING ON ONE SHOE3,403,602 10/1968 Brandon, Jr. 92/75 X 3,554,333 1/1971 Hoenick et 31..188/725 Inventor: J Maurice, Pans, France 3,456,766 7/1969 Beller188/345 [22] Filed: Feb. 5, 1971 [21] Appl. No.: 112,906 PrimaryExaminer-George E. A. Halvosa Att0meyYoung & Thompson ForeignApplication Priority Data Feb. 13, 1970 France 7005115 [57] ABSTRACT[52] US. Cl... 188/725, 60/54.6 M, 92/75,

138/345 In a disc brake having a rotary disc with brake shoes [51] Int.Cl. F1611 55/228 on o osite sides, a cylinder block for moving the 1Field of Search 106 brake shoes includes at least three pistons allarranged E, on the same side of the disc and movable perpendicu- 192/10935 AB lar to the disc, two pistons being movable in one direction andthe other piston being movable in the oppo- [56] References Cited sitedirection.

UNITED STATES PATENTS Kobayashi l88/73.4

4 Claims, 5 Drawing Figures PATENTEU UN 23 I975 SHEET 4 BF 5 mwm msm nvIIIIIIIII DISC BRAKE WITII PLURAL PISTONS ACTING ON ONE SHOE BACKGROUNDOF THE INVENTION cerns more particularly the case where such brakes areintended for motor vehicles.

SUMMARY A disc brake according to the invention is generallycharacterised in that at least three pistons are mounted in its cylinderblock, these pistons being all arranged on one and the same side of thedisc and movable perpendicularly to the latter, two in one firstdirection, the other in the opposite direction.

According to a preferred method of embodiment, two of these pistons actupon a brake shoe, the other on the transfer member.

It is thus possible to give a greater surface area to the braking shoeupon which these two-pistons act, and, consequently, other conditionsbeing equal, to reduce the wear to which such a shoe is subject.

This arrangement is particularly advantageous in the case, for example,of a disc brake intended for a heavy motor vehicle.

In addition, it is particularly suitable for the employment on anyvehicle fitted with brakes of this type, of two braking circuits, whichare independent, such as are laid down or recommended by the safetyregulations in force in certain countries.

BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of a brakeaccording to the invention, in the direction of arrow II of FIG. 2;

FIG. 2 is a cross-sectional view of this brake according to line II-IIofFIG. 1;

FIG. 3 is a cross-sectional view of this brake along the broken lineIII-III of FIG. 1;

FIGS. 4 and 5 are views similar to FIG. 3 and each relate respectivelyto an alternative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS These Figures show a disc brakeof the type comprising generally; a disc secured to the wheel or themember to be braked; a fixed support 11 in the shape of a U, extendingon either side of disc 10, and having on either side of the lattertwo'windows 12A, 12B in which braking shoes, respectively 13A, 13B aremovably mounted perpendicularly to the disc 10; a cylinder block 14fixed to the fixed support 11 facing the windows 12A, 12B of the latter,and a transfer member 15.

According to the particular embodiment shown in FIGS. 1 to 3, thesupport 11, on that side of the disc 10 which is opposite that on whichthe cylinder block 14 is arranged, has two lugs l6, 16 making itpossible to be secured by bolting to any frame, for example to thegear-box casing. The cylinder block 14 is mounted on the fixed support11 by means of screws 17, 17' perpendicular to the plane of disc 10. Thetransfer member is a ring, which is substantially flat in its centralarea and curved towards the disc on its periphery, and

it surrounds the fixed support 11, the braking shoes 13A, 13B, thecylinder block 14 and part ofthe disc 10. This transfer member or ring15 rests on three support bearings, perpendicular to the plane of thedisc 10, one of these bearings being arranged on one side of the disc 10and being formed by a tongue 20 suitably cut and folded in the supportplate of the brake shoe 13B and the other two of these bearings beingarranged on the other 'side of the disc 10, and being constituted bybosses 21, 21' of the fixed support 11. Resilient means, formed in theexample represented by a round metal wire 22 suitably formed, isinterposed between the support 11 and the transfer ring 15 for thesupport of the latter upon the three support bearings mentioned above.The ring 15 is guided perpendicularly to the plane of disc 10 bybearings 23, 24 on the one hand, and 23', 24 on the other hand, formedon the cylinder block 14 (FIG. I) and by bearings 123, 123' formed onthe fixed support 11 (FIG. 3). Resilient means, formed in the exampleshown by a suitably shaped metal blade 25, is interposed between thefixed support 11 and the braking shoe 13A; and pins 27A, 27B ensure thatthe resilient means 22, 25 mentioned above, is held in position.

In accordance with the invention, at least three pistons 30A, 30'A and30B slidably mounted in the cylinder block 14, on the same side of disc10, perpendicularly to the plane of the latter.

In the embodiments represented in FIGS-1 to 4, the pistons 30A, 30A actdirectly upon the braking shoe 13A, while the piston 30B acts upon thetransfer member or ring 15.

Pistons 30A, 30'A slide in bores 32A, 32'A hollowed out in the cylinderblock 14 parallel to each other, and piston 30B slides in a bore 32Bhollowed out in the cylinder block 14 at the end of bores 32A 32'A.

In the embodiment represented in FIGS. I to 3 the bore 328 communicatesdirectly with each of the bores 32A, 32'A through a gap 35 common tothose three bores; moreover, the axes of the three bores 32A, 32'A and32B are co-planar and are situated respectively in the mean plane of thetransfer member or ring 15, the axes of the bores 32A, 32'A beingsymmetrical with each other in relation to the axis of bore 323.

The cylinder block 14 bears a boss 36 in which a passage is hollowed outwhich open substantially into the above, pistons 30A, 30'A moveperpendicularly to the plane of disc 10, along arrow 40 of FIG. 3, andthus come to apply the braking shoe 13A against the disc 10..

At the same time, piston 30B moves in the opposite direction, and thusforces the transfer members 15 to move in a direction opposite to thatof arrow 40, said transfer member thus causing the application of theshoe 138 against the disc 10.

The disc 10 is then clamped.

When the hydraulic pressure is relaxed, the disc I0 is released.

In the method of embodiment described above, the bores 32A, 32'A, 32B ofthe cylinder block belong therefore to one and the same braking circuit.

In accordance with the embodiment represented on FIG. 4, these boresbelong to two independent braking circuits.

According to that alternative, the piston 308, which is bell-shaped, hasits concave portion facing towards the disc and is engaged so as toslide on the one hand into the bore 323 of the cylinder block 14, aspreviously, and, on the other hand, on a sleeve 45; the latter ismounted on the cylinder block 14 by means of a plug 46 secured by ascrew 47 to the said cylinder block 14 and a circlip 48 engaged in thesleeve 45 and held by the said plug 46.

A sealing ring 49 effectively seals the sliding of the piston 3013 onthe sleeve 45, while a suitable seal is also provided at the end of thesleeve 45 in contact of the latter with the cylinder block 14.

The bore 32A in which the piston 30A slides communicates with the bore328 in which piston 30B slides by means of a passage 50 which opens outin the said bore 32B inside the sleeve 45.

Similarly, the bore 32'A in which piston 30'A slides communicates withbore 328 in which piston 30B slides by means of a passage 50 which opensout into the saidbore 32B outside the sleeve 45.

With the bore 32A there is associated on the one hand a supply boss 35,and on the other hand a drain nozzle 37, as previously; jointly, withthe bore 32'A there is associated on the one hand a supply bore 35 andon the other hand a drain nozzle 37. The supply bosses 35, 35' and thedrain nozzles 37, 37 have been diagrammatically represented in dashedlines on FIG. 4; they open out in the bottom of the corresponding bores32A, 32'A.

Such a brake operates as follows:

When the two braking circuits are in operation, fluid under pressure issent simultaneously into the bores 32A, 328, the effect of which is, onthe one hand, to push the pistons 30A, 30'A in the direction of disc 10and therefore to apply the braking shoe 13A against the latter,as'previously, and, on the other hand, to push the piston 303 in thedirection of the transfer member or ring 15 and thus to give rise to theapplication of the braking shoe 138 against disc 10, as previously.

The disc 10 is then clamped.

It should be noted that in such a case the hydraulic pressure exerts itsaction on the one hand on the bottom of piston 308, by virtue of thefluid under pressure coming from the bore 32A, and on the other hand onthe side of this piston 30B,-by virtue of the fluid under pressurecoming from bore 32'A.

When the hydraulic pressure is released, the disc 10 is unclamped.

If any one of the two braking circuits should fail, that is to say ifbores 32A, for example, is no longer supplied with pressurised fluidduring an application of the brakes, the clamping of the disc may beensured by the action of the pistons 30A and 30B alone, which remaincontrolled by the other of the braking circuits.

It will be noted, moreover, that in the embodiment represented in FIG.4, the holding of the'springs 22, 25 is ensured by a single gudgeon-pin90 comprising in turn a head 91B ensuring the holding of the spring 22,a cylindrical portion 928 on which this spring 22 is engaged, acylindrical portion 93 forcibly engaged in a passage 94 of the fixedsupport 11, a portion 92A on which the spring 25 is'engaged, and a head91A which dicular to the plane of the braking disc (not shown).

The cylinder block 14 is for the purpose formed with two parallel bores62A, 62'A which each open out freely at both their ends.

Pistons 30A, 30B are slidably mounted in bore 62A in oppositedirections; the first acts directly upon the braking shoe 13A, and thesecond acts upon the transfer member or ring 15.

Along parallel axes, pistons 30'A, 30'B are slidably mounted in bore62'A in opposite directions; the former acts directly upon the brakingshoe 13A, in similar manner to piston 30A, and the second acts upon thetransfer member or ring 15, in manner similar to that of piston 308. I

These bores 62A, 62'A may belong to one and the same braking circuit,or, as an alternative, to two inde pendent braking circuits, theoperation, of the brake being in each case similar to that describedabove.

Naturally, the present invention is not limited to the formsofembodiment described and represented, but it comprises both anyalternative execution'and/or combination of their various elements, andany-alternative combination of these elements with those of the methodsof embodiment already known.

I claim:

1. A disc brake having a fixed support, a disc arranged to rotate withthe mmeber to be braked, two brake shoes arranged on either side of.this disc and movable perpendicularly to it, a cylinder block fixed tosaid fixed support, and a transfer member, said cylinder block having atleast three pistons associated with two independent braking circuits andmovably mounted therein perpendicularly to the disc, all of said pistonsbeing disposed on one side of said disc, two of said pistons actingdirectly on one of said brake shoes and a third said piston actingindirectly upon the other of said brake shoes through said transfermember, the cylinder block comprising two first parallel bores for saidtwo pistons, and a third bore for said third piston, at the end of thefirst two, said third piston also sliding on a sleeve retained againstaxial movement in said third bore, and

- the first two bores both communicating with the third,

one inside the said sleeve, and the other outside the said sleeve.

2.'A disc brake according to claim 1, in which the axes of all thepistons are coplanar.

3. A disc brake according to claim 1, in which the transfer member is asubstantially flat ring which surrounds the cylinder drive block, thebrake shoes, and a portion of the disc, the plane of the ring beingperpendicular to the disc, and the axes of the pistons being coplanarand situated in the mean plane of said ring.

4. A disc brake according to claim 1, in which said two pistons aredisposed side by side and have spaced parallel axes. I

. III I i lr

1. A disc brake having a fixed support, a disc arranged to rotate with the member to be braked, two brake shoes arranged on either side of this disc and movable perpendicularly to it, a cylinder block fixed to said fixed support, and a transfer member, said cylinder block having at least three pistons associated with two independent braking circuits and movably mounted therein perpendicularly to the disc, all of said pistons being disposed on one side of said disc, two of said pistons acting directly on one of said brake shoes and a third said piston acting indirectly upon the other of said brake shoes through said transfer member, the cylinder block comprising two first parallel bores for said two pistons, and a third bore for said third piston, at the end of the first two, said third piston also sliding on a sleeve retained against axial movement in said third bore, and the first two bores both communicating with the third, one inside the said sleeve, and the other outside the said sleeve.
 2. A disc brake according to claim 1, in which the axes of all the pistons are coplanar.
 3. A disc brake according to claim 1, in which the transfer member is a substantially flat ring which surrounds the cylinder block, the brake shoes, and a portion of the disc, the plane of the ring being perpendicular to the disc, and the axes of the pistons being co-planar and situated in the mean plane of said ring.
 4. A disc brake according to claim 1, in which said two pistons are disposed side by side and have spaced parallel axes. 